Telephone system



March 25, .1941.

R. E. KING ETAL TELEPHONE SYSTEM Filed Oct. 24, 1939 7 Sheets-Sheet l March'ZS, 1941. R. E. KING ETAL 2,235,890

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TELEPHONE SYSTEM Filed Oct. 24, 1939 7 Sheets-Sheet 5 l 346k E* A D -A Rom/er WWI/maf March 25, 1941. R. E. KING ETAL 2,235,890

TELEIHONE SYSTEM Filed oct. 24, 1959 7 sheets-sheet e dll . Rf. ffm/0 N VEN TOR; 0. ,QM/LER ATTORNEY March z5, 1941; R. E. KING ml.

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RKK/NG ORM/LER ATTORNEY Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE TELEIHGNE SYSTEM Application (lctober 24, 1939, Serial No. 300,936

8 Claims.

This invention relates to signaling systems and particularly to systems comprising impulse controlled switches.

It is the object of this invention to enable the interconnection of trunks and switches arranged for diierent types of signaling and to increase the efficiency of such signaling systems` This invention is a signaling system comprising toll lines arranged for loop and composite signaling, trunks and selectors arranged for simplex signaling, trunks and selectors arranged for loop signaling, and comprising trunks arranged for either simplex or loop signaling and for determining which type of signaling is to be used.

A feature of the invention is an incoming trunk circuit which is arranged to transmit sig nals to and receive signals from an interconnected outgoing trunk in a loop signaling circuit if the outgoing trunk is arranged only for loop signaling and which is arranged to transmit signals to and receive signals from an interconnected outgoing trunk in a simplex signaling circuit if the outgoing trunk circuit is arranged only for simplex signaling or is arrangedfor either loop or simplex signaling. l

Another feature of the invention is an outgoing trunk circuit which is arranged to receive signals from and transmit signals to an interconnected incoming trunk in a loop signaling circuit if the incoming trunk is arranged only for loop signaling and which is arranged to receive signals from and transmit signals to an interconnected incoming trunk in a simplex signaling circuit if the incoming trunk is arranged only for simplex sig- 5 naling or is arranged for either loop or simplex signaling.

A telephone system arranged in accordance with this invention is represented schematically in the drawings which form a part ofthis specification. The invention is, of course, not limited in its application to the particular system disclosed in the drawings but is applicable to any signaling system comprising lines or trunks some of which are arranged for loop signaling and others for simplex signaling and comprising automatic switches of any known type for interconnecting incoming and outgoing and two-way trunks.

Referring to the drawings:

Fig. 1 represents schematically a toll office comprising two toll lines TL-l and TL-Z arranged for composite signaling, toll line TL3 arranged for loop signaling, incoming selectors S`l and S-2 arranged for control by a simplex impulse receiving circuit, incoming selector S--3 arranged for control by a loop impulse receiving circuit, incoming trunk circuits IT--l and IT-2 interconnecting the toll lines TL-l and TL-Z with the incoming selectors S--l and S--Zy intermediate selector S-ll arranged for control by a simplex impulse receiving circuit, intermediate selectors S--E and S-6 arranged for control by loop impulse receiving circuits, toll lines TL-4 and TL-5 arranged for composite signaling, toll line TL- arranged for loop signaling, and outgoing trunk circuits OT-ll, OT-5 and OT-S connecting toll lines TL-4, TL-5 and TL--S to terminals in the banks of selectors 8 4, S-E and Si-6;

Fig.` 2 shows composite signaling circuit CX--I and other equipment associated with toll line 'FL-I;

Fig. 3 shows composite signaling circuit CX--Z and other equipment associated with toll line 'IL-2;

Fig. 4 shows incoming trunk circuit IT-l associated with signaling circuit CX|;

Fig. 5 shows incoming trunk circuit IT-2 associated with signaling circuit CX-2;

Fig. 6 shows in coming selectors S--l and S-2 associated with trunk circuits IT-l and IT-2, intermediate selector S--4 connected to terminals in the banks of incoming selectors S-I and S--2 and intermediate selector S-E connected to terminals in the banks of selector S-2;

Fig. 7 shows incoming selector S-3 associated with toll line Tir-3, and shows intermediate selector S-6 connected to terminals in the banks of selectors S-Z and .SP-3;

Fig. 8 shows outgoing trunk circuit OT-d connected to terminals in the bank of selector S-fl;

Fig. 9 shows outgoing trunk circuit OT-E connected to terminals in the banks of selectors S-ll and S-5;

Fig. 10 shows outgoing trunk circuit OT-S connecting a toll line TL-E to terminals in the banks of selectors S--5 and S-E;

Fig. 1l shows composite signaling circuit CX-.4 connecting the outgoing trunk circuit OT--4 to toll line 'IL-4; and

Fig. 12 shows composite signaling circuit CX-f-E connecting the outgoing trunk circuit OT5 to toll line Tlf-5.

The selector switches S-l, S-2, S-3, S-4,

S-5 and S- are of the well-known two-mor tion step-bystep type comprising a set of brushes, a ten-level terminal bank, and vertical and rotary stepping magnets. Reference may be had to Automatic Telephony by Smith and Campbell, 2nd edition, pages 53 to v56, for a description of the structure of such switches. The bank of each of these switches is represented in the drawings by one, two or three sets of terminals. 'Ihe relays and other apparatus associated with the selector switches S-I and S-3 are shown but the relays and other apparatus associated with selectors S--2, S-4, S-5 and S-6 are omitted. Each of selectors S-2 and S-4 is similar to the selector S-I; and each of the selectors S-5 and S-B is similar to the selector S-3. Selectors S-I, S--2 and S--4 are arranged for receiving dial impulses in a simplex circuit. Selectors S-3, S-5 and S-G are arranged for receiving impulses in a loop circuit.

The composite signaling circuits CX-I CX-2, CX-ll and CX-- are similar to the composite signaling circuits disclosed in applicants Patent No. 2,208,765 of July 23, 1940, to which reference may be had for a detailed explanation of the operation of these signaling circuits.

The operation of the various trunk circuits and selectors will be more readily described and understood by assuming calls incoming over toll lines TLP-I, TL-2 and TL--3 and outgoing over toll lines 'TL-4, TL-5 and TL-G.

cazz from tou zine T13-1 to toll zine fra- 4 Assume first a call involving t-he interconnection of .toll lines TL-I and 'TL-4. Upon seizure of toll line TL-I at its dist-ant end, the connection of signaling battery to the upper conductor of toll line TL-I effects the operative energize.- tion of the signal receiving relay I-Ill of signaling circuit CX-I. Relay .I I0 closes a circuit for operating relay II I of the associated incoming trunk circuit ITIL-I and relay I3| of the associated incoming selector S--L This circuit is traced from ground thro-ugh the front contact of relay IIII, conductor |04, winding of relay |1I.I, thence in simplex 'through resistors I|5 and IIB, windings of retard coil |20, conductors 2| and |22, outer back contacts of rel-ay |31 of selector S-I, resistors |23 an-d |29, then through resistor I3ll, the inner lower back contact of relay Il3'I and the winding of relay |3| to battery. Relay III closes va circuit for operating relay I'I2 and relay I3I closes a circuit for operating rel-ay |32. Relay |52 opens the normally closed repeater termination comprising resisto-r ||'I and capacitor |1I8 and cl-oses the talk-ing path from trunk TL-I, through repeating coil RC-I and conductors IUI and |02, to conductors |2.| and |22 leading to selector S-I. Relay ||2 also closes a circuit for operating relay I I3. Relay I-.I3 connects the winding of pad contr-ol relay |l|l4 across one end of the simplex circuit path above traced. The resi-stance of the two sides of the simplex circuit being balanced at this time, relay |I14 does not operate and the normally operated paid control relay |06 releases, thereby eiecting -the operation of relay |97, Relay |01 short-circuits the transmission pads P-II and P-l|2. Relay II3 connects ground to conductor |23 to hold selector S-I and the selected intermedi-ate select-or after these selectors have completed their selective operati-ons as hereinafter described. At its outer upper front contact, relay ,|32 closes a circuit for causing the operation of a permanent signal alarm in case dial impulses are not received over toll line 'TL-I within a predetermined interval of time. Relay |32 also connects ground to conductor |23.

When `a first train of dial impulses is received over toll line TL-I by relay IIO, relays III and I3I alternately release and reoperate in response to each impulse. Being slew in releasing, relays |.I2 and |32 de not release during the response of relays Il|-| and I 3| to dial impulses. The release of 4relay |3| in response to the first dial impulse closes .a circuit for operating relay |33 Iand vertical-stepping magnet |34, from ground at the middle upper back contact of relay |37, through the back contact of relay I3t| lower front contact of relay |32, winding of relay |33, and through the winding of the vertical-stepping magnet |34 to battery. The operation of the vertical-stepping magnet |34 steps the brushes |4| to |44, inclusive, up to `the first level of the terminal bank. The vertical off-normal springs |38 are actuated as soon `as the shaft and `brushes of the selector are moved out of normal position thereby closing a circuit, including the upper con'- tacts of springs |38 and the front contact of re lay |33, fer operating relay |35. Relay |35 .closes a locking circuit which is independent of relay |33 and includes the back contact cf the rotarystepping magnet |36 and the middle upper back contact of relay |31. When relay Il3| reoperates at the end of the first impulse, the stepping magnet |34 releases. Relay |33 is slow in releasing and remains operated until all of the impulses in the .tr-ain have been received and vertical stepping completed. The release .of relay |3| in response to each succeeding impulse of the tra-in effects the reoperation of magnet |34 to raise the brushes ystep by step to the level corresponding to the digit represented by the train of impulses.

Wh-en rel-ay .|33 releases vafter the last impulse of the train has been received, it closes a circuit including the inner front contact of relay |35 for .operating the rotary-stepping magnet |36. The operation of magnet |36 causes the release of relay |35 and rotates the brushes IM to M4, inclusive, into engagement with `the rst set of terminals in the selected level. The release of relay |35 causes the release of magnet |36. If the intermediate selector connected to the irst set of terminals is busy, the brush |413 encounters ground potential which causes the reopenation of relay |35; in which case relay |35 closes the circuit for operating the rotary-stepping magnet |33 and the brushes are advanced to the next set of terminals. Relay |35 and magnet |36 are in this manner effective Ito advance the brushes, step by step, until an idle intermediate selector is found or until the eleventh rotary position is reached due to all of Athe switches in the selected group being busy. If the brushes are advanced to the eleventh rotary lposi-tion, the springs |39 are actuated eonnecting the interrupter |5I through conductor |24 'to the winding of relay |25. Relay |25 is marginal and although its winding is normally connected in series with resistor |50 of selector S-|, the current is not sufcient to operate relay |25. Wit-h springs |39 actuated, relay |25 is operalted to intermittently connect signaling battery to the upper conductor of toll line TL-lI as an all-trunks-busy signal. 1f, however, the vbrushes of selector `S-I engage the terminals of an idle intermediate selector such as S-4, rela-y |3'I is operatively energized in a circuit from battery through the winding of relay |35, upper contact .of springs |38, back contact of magnet |36, winding of relay M1, lower normally-closed contact of the eleventh rotary-step springs |39, through conductor |23 to ground. Rel-ay |35 is marginal and does not reoperate in series with the Winding of relay |31. At its inner lower front contact, relay |31 connects conductor |23 to the test brush |43 thereby immediately guarding the selected intermediate selector from seizure by another incoming selector. Relay |31` disconnects the winding of relay |134 from conductors |12l| and |22 and connects these conductors to the brushes |44 and |42, thence through the engaged terminals to the line relay of the intermediate selector S-4. Relays |3| and |132 release in succession, relay |31 being held under control of relay lil-2 :of trunk circuit IT-Ia Relay |31 disconnect-s resistor |50- from conductor `|124- :and oonnecrts this conductor through brush |5414 to a sirnilar resistor (not shown) in the intermediate selector S-A4.

The next train of dial impulses received by signaling relay H0, are repeated to control relay of trunk circuit IT-I and to the line relay (not shown) of selectorI S-4. Theselector S-4 is similar to the selector S--l and itsv brushes 44| to 444, inclusive, are directively advanced to select a desired level and are automatically advanced to seize a set of terminals in the selected group. The call in question being one from toll line TL-l to toll line TL-4, the selector S-4 is operated to seize a set of terminals 446 connecting to an idleI outgoing trunk circuit OT--4 associated With composite signaling circuit CX-4 and toll line TL-4. Upon connection of the incoming trunk circuit IT--l through selectors S-l and S--4 to trunk OT-4, the simplex circuit path from the winding of relay of trunk circuit IT-I is extended through brushes 44| and 442 of selector S-4, conductors 12| and 122, through the windings of retard coil 120, and through resistors 1|5, 1|6, 1|1 and 'H8 to the winding of relay 1|| of trunk circuit OT-4f. Relay 1| I` operates in series with relay under control of signaling relay ||`0. Relay 1|| connects signaling battery through conductor 105, retard coil 109, the middle winding of relay 1|0 and the upper windings of retard coils 108 to the upper conductor of toll line TL--4 as a seizure signal. If additional trains of dial impulses are received over tol-l line 'IL-I, relay |l0` repeats the impulses to relay 1| I`, and relay 1|| transmits the impulses over the upper conductor of toll line 'TL-4. Since both of toll lines TL--i` and TL-4 are provided with transmission pads, the resistors ||5 and ||6 at one end of the simplex signaling path through selectors S-l and S-4 and the resistors 1|5, '||6, 1|1 and 1|8, at the other end of this path, are such that there is no difference in potential across the winding of pad control relay ||4 of trunk circuit IT--I and also no difference in potential across the winding of pad control relay 1|4 of trunk circuit OT-4. Pad control relays |06 and 106 are, therefore, both released and relays |01 and 101 are operated to short-circuit pads P--H and P--IZ associated with toll linel TL--I and to short-circuit pads P-4| and P-42 associated with toll line TL-4.

When the entire desired toll connection is completed, a signal is received over the upper conductor of toll line rIL-4 to operate relay 1|0. Relay 1I0 connects ground through conductors 104 and 124, brush 444 of selector S-4, brush |44 of selector S-|, inner upper front contact of relay |31, upper normally-closed contact of springs |39, conductor |24 to the winding of relay |25. The resistor connected to conductor 1,24 does not allow suflicient current through the winding of marginal relay |25 to effect its operation prior to the operation of relay l'|0.` When relay |25.i operates, it connects signaling battery through conductor |05, retard coil (-33, middle winding of relay ||0, upper windings of retard coils |08- to the upper conductor of toll line TL-I to indicate completion of the connection. The talking connection includes repeating coil RC-|, conductors I0| and |02, conductors |2| and |22, brushes |4| and |42, brushes 44| and 442, conductors 12| and 122, conductors 10| and 102, and repeating coil RC4. Supervisory signals received by relay ||0 are repeated by relay 1|| to toll line TL-4 and supervisory signals received by relay 1|'0 are repeated by relay |25 to toll line TL-I.

The connection is under the control of the calling toll operator or subscriber. When relay H0 releases due to release of the toll line TL-I at its distant end, it opens the circuit through the windings of relays and 1|| to cause the release of these relays and to also cause the release of relay ||2. When relay ||2 releases, it disconnects ground from conductor |23 thereby effecting the release of relay |31 of selector S-I and the release of the corresponding relay of selector S-4. The release of relay 1|| disconnects signaling battery from the upper conductor of toll line TL--4 as a disconnect signal. rFhe release of relay |31 closes a circuit for operating the release magnet |40 of selector S-l to return the brushes of this selector to normal. In like manner the selector S--4 is restored to normal.

Call from toll Zinc TL-I to toll Zine TL-5 On a call from toll line TL-I to toll line 'FL-5 the composite signaling circuit CX-L incoming trunk circuit IT-L and selectors S-I and S-4 are operated as above described except that the brushes of selector S4 are advanced to select a different group and into engagement with a set of terminals I445 which are connected to an idle outgoing trunk circuit OT-5. Upon extension of the connection from trunk circuit IT-I to trunk circuit OT5, a circuit is closed from battery through the winding of marginal relay |25, conductor |24, upper back contact of springs |39, inner upper front contact of relay |31, brush |44 of selector S|, brush 444 of selector S--4, conductor 824, and through the high-resistance upper winding of relay 825 to ground. Relay 825 operates but relay |25 being marginal does not operate. Relay 825 closes a circuit for operating relay 826. Relay 826 disconnects the lower Winding of relay 8|| from resistor B15 and completes Vthe simplex circuit path from the winding of relay of trunk circuit IT--I through brushes |4| and |42 of selector S-|, brushes 44| and 442 of selector S-4, conductors 82| and 022, left windings of repeating coil RC-52, through resistors 8|5, SIS, 8|1 and 8|8, and through the upper back contact of relay 820 to the upper winding of relay 8|l. Relay 8|| is thereupon operated in series with relay under the control of relay ||0. vRelay 8|| closes a circuit for operating the slow-to-release relay 8|2 and connects signaling battery through conductor 805, retard coil 009, middle winding of relay 8I0, upper winding-s of retard coils 808 to the upper conductor of toll line TL-E as a seizure signal. Relay 8|2 closes a locking circuit for relay 826. The marginal pad control relay 0.'.4 is bridged across the left windings of repeating coil RCD-52 and, if the simplex is unbalanced, relay 3|4 opcrates to close a circuit for holding relay 806 operated. If the simplex is balanced, relay 8|4 does not operate; in which case relay 800 releases, closing a circuit for operating relay 801. The

operation of relay 801 short-circuits the transmission pads P 5I and P 52.

Relay .8H may now respond to dial impulses, received by relay I il] over toll line TL-I and repeat these impulses over the upper conductor of toll line TL 5. When the desired toll connection is completed and relay 8i6 operates responsive to the connection of signaling battery to the distant end of the upper conductor of toll line rFIJ- 5, ground is connected through conductor 804 and the outer lower front Contact of relay 826 .to the lower, low-resistance winding of relay 825 `thereby causing the operation of marginal relay |25 of trunk circuit IT-I, and relay |25 effects the transmission of a supervisory signal over the upper conductor of a toll line TL-I to the calling operator or subscriber. Supervisory signals received over toll line TL-I by relay III) are repeated by relay 8| I to toll line 'TL-5; and supervisory signals received over toll line 'TL-5 by relay 8I0 are repeated by relay |25 to toll line TL-I. When the toll line TL-I is released at the calling end, relay H8 releases, causing the successive release of relays Ill and H2 and the successive release of relays 8H and 8l2. When relay I|2 releases, disconnecting ground from conductor |23, the selectors 5 5 and 5 4 are restored to normal as hereinbefcre described. The release of relay SII eiiects the sending of a disconnect signal over the upper conductor of toll line TL5. When the connection between relay |25 and relay 825 is opened, relay 825 releases; and, with relay SI2 released, relay 326 releases.

Call from toll Zinc TL 3 to toll line TL 6 When the toll line TL 3 is seized at its distant end byconnecting a bridge across its conductors, relay 33| of selector 5 3 operates. Relay 33| closes a circuit for operating the slow-to-release relay 332. When the first series of dial impulses are received over toll line Tlf-3, relay 33| alternately releases and reoperates in response to each impulse of the train. The rst release of relay 33| closes a circuit for operating the Vertical-stepping magnet 331 and the slow-to-release relay 333 in series. Relay 332 does not release during the response of relay 33| to dial impulses and relay 333 remains operated until all of the impulses in the series have been received. The magnet 331 operates when relay 33| releases and releases when relay 33| reoperates at Ithe end of each impulse. Each operation of magnet 331 raises the brushes 34|, 342 and 343 one step, thereby selecting the level corresponding to the number of impulses in the series. When the shaft of the switch is moved out of normal by the first operation of magnet 331, the Vertical offnormal springs 3ft@ are actuated, thereby closing a circuit including the front contact of relay 333 for operating relay 335. Relay 335 closes a locking circuit which includes the back contact of lthe rotary stepping-magnet 338. When relay 333 releases after the last impulse of the series has been received, it closes a circuit including the upper front contact of relay 335for operating `the rotary-stepping magnet 338. The operation of magnet 333 rotates the brushes into engagement with the first set of terminals inthe vselected level and causes the release of relay 335. When relay 335 releases, it causes the release of magnet 333. If the intermediate selector connected to the rst set of termin-als is busy, the guarding ground poten-tial encountered by the test brush 343 effects the reoperation of relay 335; land relay 335 closes the circuit for operating magnet 338 Ito advance the brushes to the next set of terminals. Relay 335 and magnet 338 thus cooperate to advance the brushes step by step until they engage a set of terminals connected to an idle intermediate selector. If no idle selector is available in the selected group, the brushes are advanced to the eleventh rotary position, actuating the eleventh rotary-step springs, thereby connecting the winding of magnet 331 in series with relay 336 .to a common interrupter INT. Each time the interrupter connects ground to conductor 336, relay 336 operates but magnet 331 is marginal and does not operate in series with relay 336. Each operation of relay 336 reverses the current over toll line 'TL-3 as an all-trunks-busy signal.

If and when the brushes of selector 5 3 engage a set of terminals connected to an idle intermediate selector in the selected group, the brush 343 does not encounter a guarding ground potential and ythe winding of relay 334 is operatively energized in series with relay 335. Being marginal, relay 335 does not reoperate. Relay 334 connects guarding ground potential fro-m the upper front contact of relay 332 through brush 343 to the test terminal or" the engaged set of terminals to prevent seizure by another selector having access thereto. Relay 334 disconnects Ithe toll line TL--3 from relay 33| and connects the toll line through brushes 34,2 and 332 to the selected intermediate selector. If a set of terminals 355 are seized, the associated intermediate selector 5 6 is directively operated in response to the next train of dial impulses transmitted over toll line TL 3, or if a set of terminals 343 are seized, the associated intermediate selector 5 5 is directively operated by these dial impulses. Each of the selectors 5 5 and 5 5 is similar to lthe selector 5 3. The selector 5 5 is represented in the drawings by its brushes 54|, 542, 543 and 544, two sets of terminals 545 and 546 and relay 534. The selector 5 6 is represented by it-s brushes 53|, 542 and 643 and two sets of terminals 6&5 and 645. Assruning the use of selector 5 6 on the call in question, the operation of this selector in response to the next series of impulses incoming over toll line 'IL- 3 effects the seizure of a set of terminals 645 which are connected to an outgoing trunk circuit OT 6 and toll line TL-G.

Upon seizure of the trunk circuit OT-G by a selector 5 5 and connection of the conductors of toll line 'TL-3 to conductors 92| and 922, relays Sill and SII are operatively energized in a loop signaling circuit over toll line TL 3. This circuit is traced from battery through the middle winding of relay 9H, inner lower back Contact of relay S26, lower winding of relay 9| 0, lower left winding of repeating coil RC-6, conductor 922, brush 642 of selector 5 6, brush 342 of selector 5 3, outer lower front contact of relay 33d, out over the lower conductor and back over the upper conductor of toll line TL-3, outer upper front contact of relay 334, brush 34| of selector 5 3, brush 64I of selector 5 6, conductor 52|, upper left winding of repeating coil RC b", upper winding of relay 9H), inner upper back contact of relay 926, and through the upper winding of relay 9| to ground. Relay 9I0 closes a circuit for operating the slow-to-release relay SI2. Relay 9|2 connects ground to conductor 923 to hold selectors 5 6 and 5 3, closes a circuit for energizing the lower polarizing winding of relay 9II to make this relay more quickly responsiveto incoming dial impulses, and closes a bridge including the front contact of relay 9| I, the right windings of repeating coil RC 6 and the winding of polarized relay 925 across the toll line Tlf-6 as a seizure signal. If .additional series of dial impulses are received over toll line rII.r-3, relay 9|| repeats these impulses over tol1 line TL-6. When relay 9|0 releases in response to the rst impulse of a series, it closes a circuit for operating the slow-to-release relay 9|3. Relay 9|3 remains operated until all of the impulses in the series have been received. With relay 9|3 operated, the bridge connected across toll line TL--6 each time relay 9|| reoperates includes resistor 924 instead of the right windings of repeating coil RC-6 and the winding of relay 925. Being slow in releasing, `relay 9|2 remains operated While dial impulses are being received and repeated. When the desired connection is completed, the current over toll line TL-G is reversed to cause the operation. of relay 925. Relay 925 closes a circuit for operating relay 926. Relay 926 opens the short circuit around resistor 921 to reduce the current in the polarizingwinding of relay 9|| and interchanges the connections between conductors 92| and 922 and the windings of relay 9|| so as to reverse the current over` toll line 'FL-3. The talking connection includes repeating coil RC-6. Supervisory signals incoming over toll line TL-3 are repeated by relay 9|| to tollline 'TL-6 and supervisory signals incoming over toll line TL-6 are repeated by relays 925 and 926 to toll line TL-3.

When the toll line TL-3 is released, relays 9|0 and 9|| release. The release of relay 9|0 opens the energizing circuit of relay 9|2 and the release of relay 9|| opens the bridge across toll Call from toll Zine TL-3 to toll Zine TL--5 When the toll line TL-3 is seized at its distant end, relay 33| operates. The selector S-3 is selectively operated ln response to the first series of dial impulses incoming over toll line TL-3 to select an idle intermediate selector S-5 or S6, as described on a call to toll line TL-. The intermediate selector S-5 or S-G is actuated in like manner to select an outgoing trunk circuit OT-5. Assuming connection of the toll line rIlLr--3 through selectors S-3 and S-6 to the trunk circuit OT-5, a circuit is closed for operating relay 8H. This circuit is traced from battery through the upper winding of relay H, upper back contact of relay 820, resistors BIB and 8|6, lower left winding of repeating coil RC--52, conductor 622, brush 642 of selector1 S--6. brush 342 of selector 5 3, outer lower front contact of relay 334, out over the lower conductor and back over` the upper conductor of toll line TL-3, outer upper front contact of relay 334, brush 34| of selector S-3, brush 64| of selector S-6, conductor 82|, upper left winding of repeating coil RC-52, resistor 8|5, inner upper back contact of relay 826, lower back contact of relay 820, and through the lower 75 winding of relay 8|| to ground. Since there is no circuit over conductor 824 when trunk circuit OT-5 is seized by selector S-6, relay 025 is not operatedand therefore relay 826 is not operated. Relay 8|| closes a circuit for operating relay 8|2 and relay 8|2 connects ground potential to conductor 823 to hold selectors S-6 and S-3. Relay 6H connects signaling battery to and through conductor 805 and retard coil 809 to the upper conductor of toll line TL--5 as a seizure signal. Dial impulses incoming over toll line rIL-S in a loop signaling circuit are'repeated by relay 8|| through composite signaling circuit CX-5 to toll line Til- 5.

`When the desired toll connection is completed, a supervisory signal incoming over toll line TL5 to composite signaling circuit CX5 operates re- Relay 0|0 closes a circuit through conductor '604 for operating relay 820. Relay 820 reverses the current over toll line TIF-3. Supervisory signals incoming over toll line TL-3 are repeated by relay 8| to toll line 'TL- 5 and supervisory signals incoming over toll line TL-5 are repeated by relays 6 |0 and 820 `to toll line Til-3. The talking connection includes repeating coils RC-5I and RC52. When toll line Tlf-3 is released, relay 8|| releases thereby disconnect--l ing battery from and connecting ground to the upper conductor of toll line TL-5 as a disconnect signal. When relay 8|2 releases, ground is disconnected from conductor 823 causing the return of selectors S--B and S-3 to normal in the manner hereinbefore described.

Call from toll line TL-Z to toll line TL-4 Upon seizure of ltoll line rlL--Z at its distant end, signaling battery is connected to its upper conductor causing the operation of rel-ay 2|0 of signaling circuit CX-Z. Relay 2|0 closes a circuit through conductor 204 for operating relay 2|| of the associated incoming trunk circuit IT-2. Relay 2|| closes a circuit for operating relay 2| 2. The selector S-Z is similar to the selector S-l and the windings of relays 225 and 226 .of `trunk circuit IT-Z are normally connected through conductor 224 in series with a resistor of selector S-2 similar to the resist-or |50 of selector S-|. Relay 225 is marginal and does not operate in this circuit but relay 226 is normally operated, closing a circuit for oper-ating relay 221. With relay 221 operated, the circuit for operating relay 206 is open and relay 201 is energized so that pads P2| and P-22 are normally conneoted in series with conductors 20| an-d 202. With relay 221 operated, the release of relay 2|| is ineffective to cause the operation of relay 2|3. With relays 2|| and 221 operated, a circuit is closed from ground through the lower front contact of relay 2| la lower front contact of relay 221, the winding of polarized relay 2 9, thence in a simplex circuit path through resistors 2|8, 2|1, 2|6 :and 2|5, Ithe right windings of repeating coil RC-,22, conductors 22| and 222, to rthe line relay (not shown) of selector S-2. The line relay of selector S--2 is operated by the closure of this .circuit but relay 2| 9 does not operate at this time because the current therethrough is not in the operating direction. With relays 2|2 and 221 operated, ground is connected to conductor 223 of selector S-2 to hold the selector S-2 and the succeeding intermediate selector when connect-ion is completed with :a desired outgoing trunk. The first train of impulses, incoming over toll line TL-Z .to relay 2I0, are repeated by relay 2|| to the line relay of selector S-2 and the brushes of this selector are stepped up to the desired level. The brushes are then advanced automatically to hunt for a set of terminals in the selected group which are connected to an idle intermedi-ate selector. On the call in question, a set of terminals 241 Iare selected, thereby extending the connection to the intermediate selector S-4. The next train of impulses received by relay 2I0 are repeated by relay 2I| to the line relay (not shown) of selector S-4. The brushes of selector S-4 are thereby stepped up to the desired level and automatically advanced therein into engagement with a set of terminals 446 connected to an idle outgoing toll line. tion of the terminals 446, the outgoing trunk circui-t OT-4 and associated composite signaling circuit CX-4 Iare operated as hereinbefore described to send a seizure signal over toll line 'FL-4. If additional series of dial impulses are received over toll line TL-2, relay 2I0 repeats the impulses to rel-ay 2 I I, relay 2II repeats them t0 relay 'II I and relay 'III repeats them over toll line 2L-4. Since both of toll lines T11-2 and TL--4 are equipped with transmission pads, the simplex circuit path between relay III and the winding of relay 2I9 is balanced, and the pad control relays 2I4 and 'II4 are not operated. Relays 206 and 106 are, therefore, not operated and relays 201 and '|01 are operated to short-circuit pads P-2I and P-22 and pads P-4I and P-42. The operation of relay 1I0, when the desired connection is completed, connects ground through conductors 104, conductor 124, brush 444, brush 244, lto conductor 224 to hold relay 226 and operate the marginal relay 225. Relay 225 connects signaling battery through its front contact, the back contact of relay 2I9, conductor 205, retard coil 209, middle winding of relay 2 I 0, upper Windings `of retard coils 208, to the upper conductor of toll line 'TL-2 as an answering supervisory signal. 'I'he talking path includes repeating coils RC-2l, RC-ZZ and RC-IL Supervisory signa-ls incoming over toll line rI'L-4 to relay 1I0 are repeated by relay 225 t-o toll line TL-2; and supervisory signals incoming over toll line 'YL-2 to relay 2I0 are repeated by relay 1I I to toll line TL-4. When. toll line TL- 2 is released, the release of relay 2I0 effects the release of relay 2| I; the release of relay 2| I causes the release `of relay III and relay 'III transmits a disconnect signal over toll line 'TL-4 by disconnecting battery from and connecting ground to the upper conductor of the toll line. The release of relay 2II causes the release of relay 2I2; and relay 2| 2 disconnects :the holding ground potential from conductor 223 thereby causing the return of selectors S-2 and S-4 to normal.

Call from toll line TL-Z to toll line TL-5 On a cal-1 from toll line TL-2 to toll line 'TL-5, the operation of the signaling circuit CX-Z, incoming trunk circuit IT-2 and selector S-2 is similar to that on a call to tol-l line TL-4, hereinbef'ore described, except that the iirst series of impulses received over `toll line TL-2 effect the seizure of a set of terminals 241 connected to an intermediate selector S-4 or a set of terminals 246 connected to an intermediate selector S-5. If the cal-l is routed through selector S-4, the second series of impulses received by relay 2I0 eiects the operation `of this selector to select the corresponding group of terminals and to hunt therein 'and seize :a set of terminals 445 connected to an idle trunk circuit OT-5. If the call is routed through selector S-5, the second series of impulses effects the operation of this selector Upon selecto select the corresponding group and to hunt therein and seize a set of terminals 546 connected to a trunk circuit OT--5. The selector S-S is arranged for receiving impulses in a loop circuit and is similar to selector S--3 except thatl it has a fourth conductor which is used when seized by a simplex-controlled selector, such as S2, on calls outgoing through trunk circuits, such as OT-4 or OT-5. This fourth conductor is extended to a fourth brush 544 upon operation of the cut-through relay 534 which is otherwise similar .to relay 334 of selector S3. Upon seizure of the set of :terminals 246 by the brushes of selector S-2, relay 226 of incoming trunk circuit IT-Z releases since the fourth conductor of selector S-5 is normally open. The release of relay 226 effects the release of relay 221 and the winding of relay 2I9 is thereby bridged across conductors 22| and 222 to operate the line relay (not shown) of selector S-S in a loop circuit. The -next series of impulses incoming over toll line TL-Z to relay 2I0 are repeated by relay 2| I to the line relay of selector S-5, thereby controlling this selector to select a corresponding group of terminals and to seize a set of terminals 546 :therein connected to an idle trunk circuit OT-5. The cut-through relay 534 is operated when the brush 543 engages the test terminal oi an idle trunk.

Upon connection of incoming trunk circuit IT-2 through selectors S-Z and S-5 to outgoing trunk circuit OT-5, the outgoing trunk circuit OT-5 and signaling circuit CX-5 function in similar manner to that hereinbefore described on a call from toll line TL-I. A circuit is closed through the windings of relays 225 and 226, conductors 224 and 524 and the upper high resistance winding of relay 825. Relays 226 and 825 operate but marginal relay 225 is not operated. Relay 226 closes the circuit for operating relay 221 and relay 825 closes the circuit for operating relay 826. Relays 2II, 221 and 626 complete the simplex circuit path for operating relay 8| I. Relay 0I I operates relay 8I2; and relay 8I2 closes a locking circuit for relay 826. The operation of relay 8| I connects signaling battery to the upper conductor of toll line TL-5 as a seizure signal. If additional series of dial impulses are received over toll line TL- 2, relay 2I0 repeats the impulses to relay 2| I, relay 2II repeats them to relay 8| I, and relay 8|I repeats them over toll line TL-5. The pad control relays 2I4 and 8I4 are not operated, relays 206 and 806 are not operated, and relays 20'! and 801 are operated to short-circuit pads P-ZI and P22 and pads P-5I and P-52. When the desired connection is completed, relay 8I0 operates, connecting ground to the low resistance winding of relay 825 to cause the operation of relay 225 of trunk circuit OT-2; and relay 225 effects the connection of signaling battery to the upper conductor of toll line TL--2. The talking connection includes repeating coils RC-ZI, RC-22, RC-52 and RC-5l. Supervisory signals received over toll line TL-5 by relay 8I0 are repeated by relay 225 to toll line 'TL- 2; and supervisory signals received over toll line 'TL-2 by relay 2I0 are repeated by relays 2|I and 8II to toll line TL-5. When toll line TL-Z is released, the release of relay 2I0 causes the successive release of relays 2| I and 2I2. The release of relay 2| I causes the successive release of relays 8| I, 8I2 and 826. The release of relay 2 I 2 disconnects ground from conductor 223 and selectors S-Z and S-4 or S-5 are restored to normal. The release of relay 8II disconnects signaling battery from and connects ground to `the upper conductor of tollv line TL--S as a disconnect signal.

can from wzl zine TL-z to toil me TL- On a call from toll line TL-2 to toll line 'FL-6 the operation of the signaling circuit CX-2, incoming trunk` circuit IT--2 and selector S--2 is similar to that on a call to toll line Tlf-4, above described, except that the rst route digit may be such as to eiect the seizure of a set of terminals 2% connected to an intermediate selector `S-5 or to a set of terminals M5 connected to an intermediate selector S51- 6. Relay 534 operates, relay 221 releases upon connection with selector S-5 or S--E which are arranged for loop irnpulsing, and relay 2|! repeats the next train of impulses to the line relay (not shown) of selectors S-5 or S--6 in a loop circuit. If the call is routed through selector S--5, the second series of impulses received byrelay 2|@ effect the seizure of a set of terminals M5 connected to a trunk circuit OI-6; or if the call is routed through selector S--6, the second series of impulses eiect the seizure of a set of terminals 645 connected to a trunk circuit OIL-6. Upon connection of incoming trunk circuit IIL-2 to an outgoing trunk circuit OT-, relays 226 and 221 of trunk circuit IT--Z remain normal since the selected outgoing trunk is arranged for loop signaling and has no conductor for connection to conductor 224 of selector I'I-2. With relay 221 normal, pad control relay 2u6 is operated, relay 261 is not operated and the pads P-2| and P-22 are included in the connection. A circuit is thereupon closed from battery through the middle winding of relay SI I, inner lower back contact of relay 926, lower Winding of relay Siti, lower left winding of repeating coil RCT-6, conductor 922, terminal and brush 542 of selector S--E or terminal and brush 622 of selector S-ii, terminal and brush 242 of selector 'iS-2, conductor 222, lower right winding of repeating coil PLC-22, resistor 2&6, the lowermost back contact of relay 221, winding of polarized relay 2I9, resistors 2|'I and 2I5, upper right winding of repeating coil RC-22, upper front contacts of relay 2| I, conductor 22|, brush 24| of selector S--2, brush 5ft! of selector S-5 or brush 611| of selector S6, conductor 92|, upper left winding of repeating coil RC1-6, upper winding of relay Bill, inner upper back contact of relay 926 and through the upper winding of relay 9|! to ground. Relays 9m and 9H are operated, but the polarized relay 2I9 is not operated, by the current in this circuit, Relay llill closes a circuit for operating the slow-to-release relay SI2. Relay 9|2 connects ground to conductor 923 to hold the selectors through which connection with trunk circuit OT-6 was established, closes a circuit for energizing the lower polarizing winding of relay 9H and closes a bridge including the right windings of repeating coil RC-6 and the winding of relay 25 across the toll line 'IL- 6 as a seizure signal. If additional series of dial impulses are received over toll line TL-2, relay 2&6 repeats the impulses to relay 2| I, relay ZII repeats them to relays Eilil and 9| I, and relay @Il repeats them over toil line 'TL-6. When relay SIU releases in response to the first impulse of a series, it closes a circuit for operating relay SI2. Relay M3 is slow to release and remains operated until all of the impulses in the series have been received. While relay dit is operated, the impulse bridge, connected across toll line Tlf-6 each time relay Bil reoperates, includes resistor the repeating of dial impulses.

S24 instead of the right windings of repeating coil RC-6 and winding of relay 925. Being slow in releasing, relay 9|2 remains operated during When the desired connection is completed, the current over toll line TL-S is revers-ed to operate the polarized relay S25. Relay 925 closes a circuit for operating relay 926. Relay 926 opens the short circuit around resistor 927 and interchanges the connection between the windings of relay 9H and conductors @2| and 222. The current through the winding of polarized relay 2i@ of trunk circuit IT-2 is thereby reversed to cause the operation of this relay. Relay M9 connects signaling battery to the upper conductor of toll line TIP-2. The talking connection includes repeating coils RC--2I, IEC-22 and RC--5. Supervisory signals received by relay 2|il over toli line 'TL-2 are repeated by relays 2I| and 9H to toll line IL- 6; supervisory signals received by relays 926 and 925 are repeated by relay 2l@ to toll line TL-Z. When the toll line TL-2 is released at its distant end, relay 2li) releases, causing the release of relay 2| I. The release of relay 2| causes the release of relays SIE] and 9H and the release of relay 2I9, if operated. The release of relay 2| I causes the release of relay 2132; and relay 2I2disconnects holding ground potential from conductor 223. The release of relay 9H) causes the release of relay SI2, and relay.9i2 disconnects holding ground potential from conductor 923. The release of relay 9| I opens the bridge across toll line TL- as a disconnect signal.

What is claimed is:

1. In combination, an incoming line, outgoing lines, a selector for connecting said incoming line to any one of said outgoing lines, signal repeating means associated with said incoming line for repeating signals from the incoming line to the selected outgoing line, means in one of said outgoing lines for responding to signals received over a loop circuit, means in another of said outgoing lines for responding to signals received over a simplex circuit, and circuit means including a conductor of said selector for adapting said signal repeating means to repeat the signals in a loop circuit when the selected outgoing line is one arranged to receive signals in a loop circuit and to repeat the signals in a simplex circuit when the selected outgoing line is one arranged to receive signals in a simplex circuit.

2. In combination, incoming lines, an outgoing line, selectors individual to said incoming lines, said selectors having access to said outgoing line, signal receiving means associated with said outgoing line, signal repeating means associated with one of said incoming lines for repeating incoming signals to said outgoing line in a loop circuit, signal repeating means associated with another of said incoming lines for repeating incoming signals to said outgoing line in a simplex circuit, and circuit means for adapting said signal receiving means to receive signals in a loop circuit when the incoming line from which the signals are being received is arranged to repeat the Asignals in a loop circuit and to receive signals in a simplex circuit when the incoming line from which the signals are being received is arranged to repeat the signals in a simplex circuit.

3. In a telephone system, lines, certain of said lines being arranged for composite signaling and others for loop signaling, a trunk circuit, means for interconnecting any one of said lines and said trunk circuit, said trunk circuit being arranged for either composite signaling or loop signaling.

4. In a telephone system according to claim 3, means in said trunk circuit for determining the character of the signaling for which an interconnected line is arranged.

5. In a telephone system according to claim 3, means in said trunk circuit for determining the character of the signaling for which an interconnected line is arranged and for selectively controlling the signaling arrangement of said trunk circuit.

6. In a telephone system, a line arranged for composite signaling, a line arranged for loop signaling, a trunk circuit, means for interconnecting said trunk circuit with a desired one of said lines, said trunk circuit being normally arranged for composite signaling, and means effective upon interconnection of said trunk circuit with the line arranged for loop signaling to arrange said trunk circuit for loop signaling.

7. In a telephone system, a line arranged for composite signaling, a line arranged for loop signaling, a trunk circuit, means for interconnecting said trunk circuit with a desired one of said lines, said trunk circuit being normally arranged for loop signaling, and means effective upon interconnection of said trunk circuit with the line arranged for composite signaling to arrange said trunk circuit for composite signaling.

8. In a telephone system, a trunk line, a trunk circuit individual to said line, said line and trunk circuit being arranged for composite signaling, a selector, a circuit including both of the talking conductors between said trunk circuit and said selector for repeating selective signals incoming over said line to said selector, another selector, said other selector being seizable by the rstmentioned selector, said other selector arranged for receiving selective signals in a loop circuit, and means in said trunk circuit eiective upon seizure of said other selector by said first-mentioned selector to close a loop signaling circuit for repeating selective signals to said other selector. 20

RALPH E. KING. OHMER R. MILLER. 

